Dual cassette load lock

ABSTRACT

A workpiece loading interface is included within a workpiece processing system which processes workpieces, typically wafers, in a vacuum. The workpiece loading interface includes two separate chambers. Each chamber may be separately pumped down. Thus, while a first cassette of wafers, from a first chamber is being accessed, a second cassette of wafers may be loaded in the second chamber and the second chamber pumped down. Each chamber is designed to minimize intrusion to a clean room. Thus a door to each chamber has a mechanism which, when opening the door, first moves the door slightly away from an opening in the chamber and then the door is moved down parallel to the chamber. After the door is opened, a cassette of wafers is lowered through the opening in a motion much like a drawbridge. The cassette may be pivoted within the chamber when the position from which wafers are accessed from the cassette differs from the position from which the cassette is lowered out of the chamber.

BACKGROUND

The present invention relates to a front end loading interface used in the loading of workpieces in semiconductor processing equipment.

Semiconductor processing equipment often has a plurality of chambers in which processing occurs. Arm assemblies or other robotic devices are generally used to move workpieces, generally wafers from a wafer queuing station to various chambers for processing. When the processing is finished the wafer is returned to the queuing station. For an example of prior art processing equipment, see U.S. Pat. No. 4,715,921 issued to Maher, et al. for a Ouad Processor.

Semiconductor processing is typically done in a vacuum. Therefore, a wafer queuing station into which is placed a cassette of wafers to be processed must be pumped down before the wafers may be accessed. This significantly increases the time the semiconductor processing equipment is idle while waiting for a cassette of processed wafers to be exchanged for a cassette of unprocessed wafers and subsequent pumping down of the wafer queuing station.

SUMMARY OF THE INVENTION

In accordance with the preferred embodiment of the present invention, a workpiece loading interface is presented for inclusion within a workpiece processing system. The workpiece loading interface includes two separate chambers. Each chamber may be separately pumped down. Thus, while a first cassette of workpieces, typically wafers, from a first chamber are being accessed, a second cassette or wafers may be loaded in the second chamber and the second chamber may then be pumped down. This can significantly increase throughput of wafers through the workpiece processing system.

In the preferred embodiment, each chamber is designed to minimize intrusion to a clean room. Thus a door to each chamber has a mechanism which, when opening the door, first moves the door slightly away from an opening in the chamber and then the door is moved down parallel to the chamber. After the door is opened, a cassette of wafers is lowered through the opening in a motion much like a drawbridge. The cassette of wafers is on a support with no side panels, facilitating the replacement of a cassette of processed wafers with a cassette of unprocessed wafers by an automated device.

The cassette may be pivoted within the chamber when the position from which wafers are accessed from the cassette differs from the position from which the cassette is lowered out of the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top view of a block diagram or semiconductor processing equipment which includes two cassette load locks in accordance with the preferred embodiment of the present invention.

FIG. 2 shows a block diagram of a load lock which is part of the semiconductor processing equipment shown in FIG. 1 in accordance with the preferred embodiment of the present invention.

FIG. 3 shows a second block diagram of the load lock shown in FIG. 2 in accordance with the preferred embodiment of the present invention.

FIG. 4 shows another block diagram of the load lock shown in FIG. 2 in accordance with the Preferred embodiment of the present invention.

FIG. 5 is a block diagram or a cassette wafer holder in a position extended out of the load lock shown in FIG. 2 in accordance with the preferred embodiment of the present invention.

FIG. 6 is a block diagram of the cassette wafer shown in FIG. 5 in an upright position within the load lock shown in FIG. 2 in accordance with the preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, a top view of semiconductor processing equipment 1 is shown. Semiconductor processing equipment 1 may be used, for example, for etching wafers.

Semiconductor processing equipment 1, includes, for example, a processing chamber 3, a processing chamber 4, a processing chamber 5 and a processing chamber 6. A central chamber 2 may be used to temporarily store wafers on robotic equipment 7 when wafers are being moved to or from various of the processing chambers.

Semiconductor processing equipment 1 also includes dual cassette load locks. In chamber 8, a wafer cassette 16 holds wafers 10. In chamber 9, a wafer cassette 17 holds wafers 11. Wafer tray 17 pivots around a pivot point 15. When wafers 11 from tray 17 are accessed by semiconductor processing equipment 1 for processing, wafer tray 17 is flush against a gate 13, as shown, and easily accessed by robotic equipment 7 for transportation into central chamber 2. When wafer tray 17 is ready to be removed from chamber 9, wafer tray 17 is pivoted back from gate 13 in preparation for the opening of chamber 9 and removal of wafer tray 17.

Similarly, wafer tray 16 pivots around a pivot point 14. When wafers 10 from tray 16 are accessed by semiconductor processing equipment 1 for processing, wafer tray 16 is flush against a gate 12 and easily accessed by robotic equipment 7 for transportation into central chamber 2. When wafer tray 16 is ready to be removed from chamber 8, wafer tray 16 may be pivoted back an angle 18 from gate 12, as shown, in preparation or the opening of chamber 8 and removal or wafer tray 16. In the preferred embodiment, angle 18 is about twenty-one degrees.

Chamber 8 and chamber 9 may be separately and individually pumped down. A vacuum pump 19 is able to provide a vacuum in chamber 8. A vacuum pump 20 is able to provide a vacuum in chamber 9. In FIG. 1, vacuum pumps 19 and 20 are shown in schematic form. Typically pumps 19 and 20 would reside within semiconductor processing equipment 1. Further, while FIG. 1 shows two separate pumps, a single pump could be used to separately and individually pump down chamber 8 and chamber 9.

FIG. 2 shows a simplified block diagram front view of wafer chamber 8. In the preferred embodiment, the volume of chamber 8 is 46 liters. A door 21 is shown in a closed position. Door 21 includes an observation window 22. Door 21 is opened and closed using a pneumatic actuator within a rod 24. Magnets in the pneumatic actuator interface attract an outer ring 26. Outer ring 26 is connected to door 21 through an assembly 23.

FIG. 3 shows door 21 lowered into an open position. An opening 25, for example, may be fifteen inches high and ten and one half inches wide. By opening down, the intrusion of door 21 into a clean room may be minimized. In the preferred embodiment the total intrusion is about one inch.

Once door 21 is lowered, wafer tray 16, on a support structure 43, may then be lowered out of chamber 8, much like a draw bridge is lowered at a castle entrance. Wafer tray 16 may then be removed and a new wafer tray placed upon support structure 43. Support structure 43 is designed with a hollow bottom so that when door 21 is opened and wafer tray 16 is lowered, a laminar airflow may sweep downward through wafers 10.

In FIG. 4, additional detail of the mechanism which controls the opening and shutting of door 21 is shown. A side panel 31 of door 21 is connected to a carriage 30 by a spring 34, a link 36 and a link 35. As controlled by the pneumatic actuator within rod 24, door 21 travels up and down parallel to a rail 50. When being closed, door 21 is stopped by an abutment 32; however, carriage 30 continues upward, expanding spring 34, until a gap 33 is completely closed. While carriage 30 continues moving upward, a pivot 39 connected to link 36, and a pivot 40 connected to link 35 continue moving upward. However, a pivot 37 connected to link 36 and a pivot 38 connected to link 35 cause door 21 to move towards carriage 30. Therefore, as gap 33 is closed, links 35 and 36 translate the upward motion of carriage 30 into horizontal motion of door 21. Door 21 is thus brought snug against, and hence seals chamber 8.

When door 21 is opened, spring 34 compresses causing gap 33 to reappear and links 35 and 36 to 20 straighten, thus moving door 21 horizontally away from chamber 8.

FIGS. 5 and 6 show a block diagram of one possible implementation of an assembly for guiding the lowering and raising of support structure 43. In FIG. 5, support structure 43 and cassette 16 are shown lowered out of chamber 8. A roller 44 connected to support structure 43 is shown resting on an extension of a cam containing slot 46 within chamber 8. A roller 45, also connected to support structure 43, is shown at a first end of a slot track 46.

In FIG. 6, support structure 43 and cassette 16 are shown in the upright position within chamber 8. In this position, wafers 10 are horizontal and are stacked so that they are ready to be accessed by semiconductor processing equipment 1. When sup port structure 43 and cassette 16 are in the upright position, roller 45 is rolled to a second end of slot track 46 and roller 44 rests against a stop 49. Stop 49 is an extension so the cam which contains slot 46. 

1-4. (canceled)
 5. In a work piece processing system, a method for closing and sealing a chamber, comprising: a) providing a chamber having an opening formed through a surface of the chamber adapted to allow work pieces to be received from outside the chamber and a door adapted to seal against the surface so as to close the opening; b) moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface; and c) moving the door linearly horizontally a distance toward the opening so as to cause the door to contact and seal against the surface of the chamber and close the opening.
 6. The method of claim 5, further comprising: providing a carriage, the carriage being horizontally stationary and adapted to move parallel to the chamber surface, and a link between the door and the carriage, the link permitting linear horizontal movement of the door.
 7. The method of claim 6, wherein providing a carriage, the carriage being horizontally stationary and adapted to move parallel to the chamber surface, and a link between the door and the carriage, the link permitting linear horizontal movement of the door comprises: providing a four-bar linkage comprising the carriage, the door, and a link between the carriage and the door.
 8. The method of claim 6, wherein providing a carriage, the carriage being horizontally stationary and adapted to move parallel to the chamber surface, and a link between the door and the carriage, the link permitting linear horizontal movement of the door comprises: providing a rail, oriented parallel to the chamber surface, along which the carriage is adapted to move and which is adapted to substantially prevent horizontal motion of the carriage.
 9. The method of claim 8, wherein providing a rail along which the carriage is adapted to move and which is adapted to limit horizontal motion of the carriage comprises: providing a rail fixedly coupled to the chamber.
 10. The method of claim 6, further comprising providing an abutment adapted to limit parallel motion of the door while the link converts parallel motion of the carriage into linear horizontal motion of the door.
 11. The method of claim 10, wherein providing an abutment adapted to limit parallel motion of the door while the link converts parallel motion of the carriage into linear horizontal motion of the door comprises: providing an abutment adapted to contact a portion of the door and thereby block further motion of the door parallel to the chamber as the carriage continues to move parallel to the chamber.
 12. The method of claim 11, wherein providing an abutment adapted to contact a portion of the door and thereby block further motion of the door parallel to the chamber as the carriage continues to move parallel to the chamber comprises: providing an abutment along which the door portion is adapted to move while moving linearly horizontally.
 13. The method of claim 12, further comprising providing an extensible spring coupled between the carriage and the door portion adapted to bias the door portion against the abutment as the carriage continues to move parallel to the chamber.
 14. The method of claim 10, wherein providing an abutment adapted to limit parallel motion of the door while the link converts parallel motion of the carriage into linear horizontal motion of the door comprises: providing an abutment fixedly coupled to the chamber.
 15. The method of claim 6, wherein moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface comprises: urging the carriage along a rail oriented parallel to the chamber surface so as to cause the door to move parallel to the chamber surface.
 16. The method of claim 6, wherein moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface comprises: biasing the link so as to cause the link to retract the door linearly horizontally so as to provide a friction-preventing gap between the door and the chamber surface during parallel motion of the door.
 17. The method of claim 5, further comprising: d) causing a portion of the door to contact and move linearly horizontally against an abutment.
 18. The method of claim 17, wherein causing a portion of the door to contact and move linearly horizontally against an abutment is performed after moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface; and is performed during moving the door linearly horizontally a distance toward the opening so as to cause the door to contact and seal against the surface of the chamber and close the opening.
 19. The method of claim 5, further comprising: d) after performing moving the door linearly horizontally a distance toward the opening so as to cause the door to contact and seal against the surface of the chamber and close the opening, opening and unsealing the chamber by moving the door linearly horizontally a distance away from the opening so as to cause the door to break contact with and unseal from the surface of the chamber, and then again moving the door parallel to the chamber surface, wherein the moving door does not experience surface friction as the door moves parallel to the chamber surface.
 20. A door assembly for opening and closing an opening through which a chamber receives and discharges work pieces, comprising: a door adapted to close and seal an opening through which a chamber receives and discharges work pieces; a horizontally stationary carriage; and a link coupled between the door and the horizontally stationary carriage so as to permit linear horizontal movement of the door toward or away from the opening.
 21. The door assembly of claim 20, wherein the door, the carriage, and the link comprise a four-bar linkage.
 22. The door assembly of claim 20, wherein the carriage is adapted to move parallel to a chamber surface through which the opening is formed, and wherein the link is adapted to convert parallel motion of the carriage into linear horizontal motion of the door toward or away from the opening.
 23. The door assembly of claim 22, further comprising an abutment, and wherein a portion of the door is adapted to contact and move against the abutment, and wherein the door is supported by the carriage such that the door is adapted to move with the carriage parallel to the chamber surface sufficiently to cause the door portion to contact the abutment.
 24. The door assembly of claim 23, wherein the abutment is fixedly coupled to the chamber.
 25. The door assembly of claim 23, wherein the abutment is adapted to block the door from moving further parallel to the chamber surface while the door portion contacts the abutment, and wherein the door portion is adapted to move linearly horizontally against the abutment while the carriage continues to move parallel to the chamber.
 26. The door assembly of claim 25, further comprising a spring coupled between the carriage and the door portion and adapted to bias the door portion against the abutment while the carriage continues to move parallel to the chamber surface.
 27. The door assembly of claim 26, wherein the door is supported by the carriage such that the door is adapted to move with the carriage parallel to the chamber surface, and further comprising a spring coupled between the carriage and the door portion and adapted to bias the link, and wherein the link is adapted when biased by the spring to retract the door linearly horizontally so as to provide a friction-preventing gap between the door and the chamber surface during said parallel motion of the door.
 28. The door assembly of claim 27, wherein the door portion is a panel fixedly extending from a side of the door.
 29. The door assembly of claim 20, wherein the door is supported by the carriage such that the door is adapted to move with the carriage parallel to the chamber surface, and further comprising a spring coupled between the carriage and the door and adapted to bias the link, and wherein the link is adapted when biased by the spring to retract the door linearly horizontally so as to provide a friction-preventing gap between the door and the chamber surface during said parallel motion of the door.
 30. The door assembly of claim 22, further comprising a horizontally-stationary rail oriented parallel to the chamber surface along which the carriage is adapted to move.
 31. The door assembly of claim 30, wherein the rail is fixedly coupled to the chamber. 